This invention relates generally to coating composition and a process for providing a chrome finish onto substrates. Particularly, the invention relates to a metallic coating composition and a process for vacuum metalizing chromium onto various substrates. Specifically, this invention relates to a two step vacuum metalization process for chroming aluminum, steel, plastic and other substrates for automotive parts, for example, for providing a chrome layer on automotive parts such as vehicle wheels, hub caps, bumpers, interior and exterior trim, knobs, handles and other parts.
The metalization process of the present invention has specific and sequential steps to produce chromed automotive and other parts having superior chrome adhesion characteristics to prevent delamination and having chemical and road hazard resistant qualities. Although the disclosure herein discusses the process of metalizing chromium in the production of vehicle wheels, other chroming processes as well as the chroming of other metallic and nonmetallic substrates are within the purview of this invention.
In the past, aluminum and steel vehicle wheels, for example, have traditionally been electroplated to produce chrome wheels. These prior art processes require the wheel rim to be polished to provide a very smooth surface for the chrome plating to be effective. Further, the wheels are pretreated in hazardous chemicals to provide a clean and homogeneous surface for adherence of the chrome plating. The wheels are then coated with up to three different metal coatings with each step requiring the wheel to be submerged in hazardous solutions. The failure rate of these prior art processes is generally high. Additionally, should the chrome plated surface be damaged, corrosion or rust will typically begin rapidly, causing the chrome plating to delaminate from the wheel surface.
Another alternative prior art process has been developed which applies the chrome coating by vacuum metalization, thereby eliminating the application of the decorative coating using hazardous solutions. This prior art process entails applying one or two primer coat compositions to provide a smooth surface and to provide a suitable adhesion for the Cr to be applied. The wheel is then placed into a vacuum metalization chamber where a decorative coating is applied. Subsequently, a coating is applied to protect the metalized layer from environmental elements. The process produces chrome-like finishes on wheels, but not equal to the quality of the plating process and as such has not been accepted by the wheel manufacturers in the United States.
The present invention overcomes the difficulties and the shortcomings of the prior art. An object of the present invention is to provide a true chrome finish on wheels and other parts that are resistant to harsh climatic conditions. A further objective is to eliminate hazardous materials used during the application process and to greatly reduce the potential for delamination should the coating be damaged, impacted or scratched, as has been problematic in the prior art. This process is also applicable to any substrate where a durable, decorative, chrome finish is desired on automotive parts, for example, on vehicle wheels, bumpers, hub caps, and the like. Particularly, the object of the invention is to provide a vacuum metalization process for chroming metal and other substrates, such as aluminum and steel substrates, for example.